As CMOS technology using silicon is getting close to a limit of fine processing, alternative channel materials have been searched for extending the lifetime of the technology. As most promising candidates of such materials, attention is drawn to nanocarbon materials represented by carbon nanotube and graphene, on which various research and development have been conducted.
It is expected that new information processing concepts may be discovered through research and development of nanocarbon materials, which go beyond CMOS technology, such as spintronics. Results ever obtained include spin injection into carbon nanotube and graphene at room temperature, long spin relaxation with order of μm, and the like, with which various properties are observed that are suitable for spintronics materials.
A spin filter is considered to be a basic device in spintronics for obtaining spin-polarized current. In recent years, a spin filter is proposed that uses a zigzag graphene nanoribbon with an even number of rows having a magnetic moment. By forming two electrodes using zigzag graphene nanoribbons with an even number of rows having magnetic moments, and having magnetic moment directions of the electrodes be antiparallel with each other, a spin filter can be formed in which only electrons having spin in one direction are conducted.